Because of heat resistance, freeze resistance, oil resistance, fuel oil resistance and compression recovery, fluorosilicone rubber is widely used as parts for automobiles, aircraft and other transporting vehicles and parts for petroleum-related equipment. When used as automobile parts, especially turbocharger hoses, fluorosilicone rubber is often molded into a two-layer structure of dimethylsilicone rubber and fluorosilicone rubber. Specifically, on the hose inner side where oil resistance is required, fluorosilicone rubber is selected. On the hose outer side, dimethylsilicone rubber is selected for restitution and wiping resistance. This results in a whole hose having a two-layer structure of fluorosilicone rubber and dimethylsilicone rubber. However, due to a difference in compatibility between fluorosilicone rubber and dimethylsilicone rubber, the structure shows very poor adhesion at the interface when processed by steam vulcanization and hot air vulcanization (HAV) using a low pressure during molding, leaving a likelihood of interfacial separation. In press molding and similar molding processes capable of applying a certain pressure during molding, co-vulcanization occurs at the interface to achieve co-adhesion, reducing the likelihood of interfacial separation. For the molding of hoses, however, steam vulcanization and HAV processes are adequate.
Thus there exists a demand for a fluorosilicone rubber composition which is improved in interfacial adhesion to dimethylsilicone rubber when processed by steam vulcanization and HAV using a low pressure during molding, and a fluorosilicone rubber composition which can be blended with a dimethylsilicone rubber composition at any proportion while restraining the risk of interlaminar peeling or delamination in a microscopic region.
Reference should be made to JP-A 2002-317885, JP-A 2001-002923 (U.S. Pat. No. 6,369,155), JP-A 5-186700 (U.S. Pat. No. 5,342,879, EP 551211), and JP-A 2000-026735.